. Bulletin. Natural history; Natural history. 42 Illinois Natural History Survey Buixetin than the year before. In 1926 it increased markedly on all except rye, reaching the greatest degree recorded during the survey. It is evident from an inspection of Figure 3S that the climatic conditions of any one year have not aflfected the prevalence of stem rust to the same extent, or in the same way, on every crop. The intensities of attack, as indicated by the indexes of destruc- tiveness calculated from the field data, are shown in Figure 39. Prac- tically the same tendencies are exhibited on all th
. Bulletin. Natural history; Natural history. 42 Illinois Natural History Survey Buixetin than the year before. In 1926 it increased markedly on all except rye, reaching the greatest degree recorded during the survey. It is evident from an inspection of Figure 3S that the climatic conditions of any one year have not aflfected the prevalence of stem rust to the same extent, or in the same way, on every crop. The intensities of attack, as indicated by the indexes of destruc- tiveness calculated from the field data, are shown in Figure 39. Prac- tically the same tendencies are exhibited on all the crops, wheat alone showing a marked divergence. In 1924, when the trend of destruc- tiveness was upward on the three other crops, it declined very markedly on wheat. There has been a distinct parallel between prevalence and destruc- tiveness throughout the five seasons, the only break in it being the at- tack on wheat in 1923, in which year the increase in prevalence over the previous season was accompanied by a large decrease in destructiveness. Fig. 39. Destkuctiveness of stem rust ox the cereal crops, 1922-1926 The indexes of destructiveness given in tables in the text are shown graph- ically here. The trend of destructiveness from year to year follows very closely the trend of prevalence (compare with Fig. 38), being greatest In 1926 and 1922, and generally very low in the other Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Illinois. Natural History Survey Division. Urbana, State of Illinois, Dept. of Registration and Education, Natural History Survey Division
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Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
